A downhole sucker rod pumping unit

ABSTRACT

The invention relates to downhole sucker rod pump assemblies comprising a stationary flexible long-length tube having disposed therein a movable flexible long-length rod, connected at opposite ends to a surface drive and to an operating element of a submersible piston pump or screw pump. An annulus between the rod and the tube is filled with a lubricant from a channel at the wellhead end. The lower and upper ends of the tube are connected to a wellhead pipe and a pumping pipe. At the lower end of the rod is a box filled with a liquid which provides protection for the seal of a plunger pump. The flexible long-length rod is capable of rotating or reciprocating movement. The result is an increase in the operating reliability of a deep-well pump, an increase in the time between repairs and a decrease in the energy consumed when the pump is operating.

FIELD OF THE INVENTION

The invention relates to deep well sucker rod pumping units such as plunger and progressing cavity pumps with sucker rod drives to lift fluids from deep wells especially from heavily deviated ones.

PRIOR ART

Known is a sucker rod drive for downhole pumping units produced by the USA company Weatherford under the name COROD (www.weatherford.com/corod) and Canadian company PRO-ROD (www.prorod.com) which is an indivisible long flexible rod completely replacing the string of sectional rods and is as long as the running depth of a deep well displacement pump. If a sucker rod plunger pump is used a long flexible rod through the polished rod is connected to a reciprocal mover by its upper end, say to a conventional pumping unit, while by its other end it is connected to a sucker rod plunger pump directly or through a rod adapter. In addition, to operate submerged plunger pumps Weatherford produces long flexible rods with elliptical cross-section to reduce intensity of distributed load from the rod to tubing. If a progressing cavity pump is used a long flexible rod is connected to a twist mover by its upper end, while by its other end it is connected to a progressing cavity pump directly or through a rod adapter. Though long flexible rods are expensive and require additional equipment their trips into and out of the well take a short time. The absence of sucker rod couplings leads to greatly reduced tubing wear as a result of their rubbing against tubing by a thickened sucker rod couplings. In some heavily deviated wells the use of long flexible rods is the only proper way to lift borehole fluids to the surface.

The disadvantage of the above long sucker-rod drive for deep-well pumping units is that tubing wear remains high anyway due to ingress of solids, such as sand, between interacting surfaces of a long flexible rod and inner surface of tubing. Besides, borehole fluid is not a good lubricate for interacting surfaces.

Most close in terms of its technical essence and the result to be achieved is a deep well sucker rod pumping unit consisting of a tubing string installed oil well sucker rod pump the driven operating element of which is connected with the string of hollow rods interconnected in tandem by detachable joints. Each rod cavity is isolated, contains sealing plugs with formation of adapters for detachable joints, vacuumized or gas filled. The rods are made of metal of low specific weight and protected from corrosion. (RU2235905 dated Jul. 5, 2003).

The disadvantage of the deep well sucker rod pumping unit chosen as a prototype is its high price, increased wear of interacting parts of sucker rods and tubing.

The aim to be achieved by this invention is complete isolation and protection of the interacting pair—endless rod and internal surface of tubing—from the negative effect of borehole fluid and its ingredients, allocation of lubricating liquids (oil) between interacting surfaces.

The technical result is to achieve increased reliability of a borehole pump, increased overhaul life, reduce power consumption for deep-well sucker rod operation.

SUMMARY OF THE INVENTION

The aim stated and the technical result can be achieved due to the fact that the downhole sucker-rod pumping unit comprising a surface power drive and tubing string with a mounted borehole pump the driven operating element of which is joined to the sucker rod drive, in accordance with invention, a rod drive design comprising the fixed flexible tube inside of which there is a movable flexible rod with one of its end connected to the surface power drive by the wellhead polished rod, and with the other end to the driven operating element as a plunger of the borehole pump by the pumping polished rod, the entry and exit points of the movable flexible rod and fixed flexible tube are sealed, the annular space between them is filled with a lubricating fluid with the channel at the wellhead end, the lower and upper ends of the fixed flexible tube are connected with the wellhead and pumping pipe branches the length of which is longer than the maximum plunger pump stroke, and the upper end of the wellhead pipe branch being attached to the sealing unit of the pumping polished rod rigidly connected by the lower end and by means of the packing unit with the bucket filled with the fluid the specific weight of which is higher than that of a pumped out fluid possible to house the sealing unit of the polished rod in any position.

In addition the above stated aim and the technical result can be achieved due to the fact that the downhole sucker-rod pumping unit comprising a surface power drive and tubing string with a mounted borehole pump the driven operating element of which is joined to the sucker rod drive, characterized in that a rod drive design comprising the fixed flexible tube inside of which there is a movable flexible rod with one of its end connected to the surface power drive by the wellhead polished rod, and with the other end—to the driven operating element as a shaft of the progressing cavity by the pumping polished rod, the entry and exit points of the movable flexible rod and fixed flexible tube are sealed, the annular space between them is filled with a lubricating fluid with the channel at the wellhead end, the lower and upper ends of the fixed flexible tube are connected with the wellhead and pumping pipe branches and, the upper end of the wellhead pipe branch being attached to the sealing unit of the pumping polished rod and with the upturned bucket filled with the lubricating fluid. The annular space filled with the lubricating fluid of the additional channel to create an excess pressure. The connection of the annular space filled with the lubricating fluid with the cavity of the upturned bucket by means of the bypass valve calibrated for a design pressure.

BRIEF DESCRIPTION OF THE DRAWINGS

The FIG. 1 shows the down-hole sucker rod plunger pumping unit with spacer fluid in the bucket on the sliding flexible rod in the plunger upper position.

The FIG. 2 shows the down-hole sucker rod plunger pumping unit with spacer fluid in the bucket on the sliding flexible rod in the plunger lower position.

The FIG. 3 shows the down-hole sucker rod plunger pumping unit with the upturned bucket on the fixed flexible tube.

The FIG. 4 shows down-hole sucker rod progressing cavity pumping unit with the upturned bucket on the fixed flexible tube.

The FIG. 5 shows the down-hole sucker rod plunger pumping unit with the double-channel coiled tubing.

The FIG. 6 shows the down-hole sucker rod progressing cavity pumping unit with the independent lifting channel.

DESCRIPTION OF THE BEST EMBODIMENT

A down-hole sucker rod plunger pumping unit consists of (FIGS. 1&2) a fixed long flexible tube 1 inside of which there is a movable long flexible rod 2. The fixed flexible tube 1 is inside the tubing string 3. The adapter 4 connects the lower part of the fixed long flexible tube 1 with the upper end of the pumping nipple 5 which is longer than the maximum plunger 28 stroke of the deep well pump 29 by the design variable. The lower end of the pump nipple 5 is connected with the packing unit 6 in which there is the seal 7 of the pumping polished rod 8. The pumping polished rod 8 is connected with the sliding long flexible rod 2 directly by a standard joint or sleeve 9. The body of the sliding flexible rod 2 is possible to be threaded for sleeve 9 to simplify its location inside the fixed flexible tube 1. The lower end of the pumping polished rod 8 has a rigid connection with the bucket 10 by means of the connecting point 11. The outside diameter of the bucket 10 is less than the inner diameter of the tubing string 3, while the inner diameter of the bucket 10 is bigger than the outside diameter of the pumping nipple 5. The bucket 10 is filled with spacer fluid 12 of high specific weight and immiscible with borehole fluid 13, such as mercury. The length of bucket 10 and volume of spacer fluid 12 are such that in any position of the polished rod 8 spacer fluid 12 covers the packing unit 6 and serves as its protection from the contact with borehole fluid 13.

For bleeding of spacer fluid 12 there on the surface in the connecting unit 11 is the bleeder valve 14. The lower part of the connecting unit 11 is attached to the adapter rod 15 which in turn is connected with the plunger 28 of the downhole pump 29. As an alternative, to protect the packing unit 6 from the contact with borehole fluid 13 (FIG. 3) the upturned bucket 36 rigidly connected with the fixed long flexible tube 1 and filled with lubricating fluid 23 is used. Between the pipe branch 5 and upturned bucket 36 there is the calibrated valve 37 which will open when the rating pressure of lubricating fluid 23 in the fixed flexible tube 1 is reached to allow the fluid 23 flow into the upturned bucket 36 thus making it possible either to add or completely replace lubricating fluid 23 in the cavity of the upturned bucket 36. Taking into account that the specific weight of lubricating fluid 23 is less than that of borehole fluid 13, lubricating fluid 23 will always be locked in the upturned bucket 36 thus providing bath of lubricating fluid 23 for the other end of the packing unit 6. The volume of fluid 23 in the upturned bucket 36 is controlled at the wellhead by pump operation. The fluid level 38 (the contact surface of lubricating fluid 23 and borehole fluid 13) is controlled by the lower shear of the upturned bucket 36. In case a tubing sucker rod pump is used as the downhole pump 29 the connecting unit 11 can contain a collet pipe coupling (not shown), while in case a rod pump is used as the downhole pump 29 the collet pipe coupling is right on the rod pump (not shown). The adapter 16 connects the upper part of the fixed long flexible tube 1 (FIGS. 1&2) with the lower end of the wellhead nipple 17 which is longer than the maximum plunger 28 stroke of the oil well pump 29 by the design variable. The upper end of the wellhead nipple 17 is connected with production wellhead 25 on which there is the packing unit 18 containing the seal 19 of the wellhead polished rod 20. The wellhead polished rod 20 is connected with the sliding long flexible rod 2 via a standard joint or sleeve 21. The annular space 22—between the fixed long flexible tube 1 and sliding long flexible rod 2—is filled with lubricating fluid 23, with the annular space 22 having an access to the wellhead as a channel 24 to refill lubricating fluid 23 or producing an excessive pressure in the annular space 22. The long flexible rod 2 can be shop-mounted inside the long flexible tube 1, with lubricating fluid 23 being in the annular space 22, with installation of wellhead 17 or 40 and pumping 5 or 34 nipples with the packing units 6, 18 or 41, calibrated valves 37 and buckets 10 or 33 or 36 and can be run into the well as a unified system. Spacer fluid 12 is filled into the bucket 10 right at the wellhead before running into the well. To decrease wear of sliding elements centralizers (not shown) can be mounted at the reference points of the fixed long flexible tube 1, sliding long flexible rod 2 and bucket 10. Adapters 4 and 16 can be attached to the sliding long flexible rod 2 by welding, glue or mechanically (press fit or others). The inner cavity of the plunger 28 which is in the box of the downhole pump 29 is connected with the inner cavity 30 of tubing string 3 through the opening 27.

A downhole sucker-rod pumping unit with a progressive cavity pump consists of (FIG. 4) a fixed long flexible tube 1 inside of which there is a sliding long flexible rod 2. The fixed long flexible tube 1 is inside the tubing string 3. The lower end of the pump nipple 34 is connected with the packing unit 6 in which there is the seal 7 of the pumping shaft 39. The pumping shaft 39 is connected with the sliding long flexible rod 2 directly by a standard joint or sleeve 9 and with the shaft 31 of the progressive cavity pump 32 by the sleeve 26. To protect the packing unit 6 from its contact with borehole fluid 13 the upturned bucket 33 is used which is rigidly connected with the fixed long flexible tube 1 and filled with lubricating fluid 23. The other alternative for protection of the packing unit 6 from its contact with borehole fluid 13 (not shown) suggests to use the bucket 10 rigidly connected with the fixed long flexible tube 1 and filled with spacer fluid 12. Taking into account that the sliding long flexible rod 2 rotates the bucket 10 can be of smaller size as compared with the plunger alternative and with less volume of spacer fluid 12 herein. Between the pipe branch 34 and upturned bucket 33 there is the calibrated valve 37 which will open when the rating pressure of lubricating fluid 23 in the fixed flexible tube 1 is reached to allow its flow into the upturned bucket 33 thus making it possible either to add or completely replace lubricating fluid 23 in the cavity of the upturned bucket 33. The upper end of the wellhead branch pipe 40 is connected with the production wellhead 25 at which there is the packing unit 41 containing the seal 42 of the wellhead shaft 43. The annular space 22—between the fixed long flexible tube 1 and sliding long flexible rod 2—is filled with lubricating fluid 23, with the annular space 22 having an access to the wellhead as a channel 24 to refill lubricating fluid 23 or producing an excessive pressure in the annular space 22. The body of the sliding flexible rod 2 is possible to be threaded for sleeve 9 to simplify its location inside the fixed flexible tube 1. The actuator 35 to rotate the sliding long flexible rod 2 is at the wellhead. Outside the fixed long flexible pipe 1 there can be arranged and attached to it, say by clamps (not shown) a heater cable, capillary line to supply chemicals to the pump suction, electrical cables, wires and/or hydraulic channels. Instead of the fixed flexible tube 1 it is possible to use a multichannel long flexible tube, such as double-channel 46 where in one of the channels there is the sliding long flexible rod 2, while the other one is used as a lifting string (FIG. 5) or, as another alternative, the sliding long flexible rod 2 with the fixed long flexible tube 1 inside it can be located outside the lifting string 44 (FIG. 6), say as the tubing string 3, and be attached to it, say by clamps. To connect both channels and the downhole pump 29 or 32 the connecting adapter 45 is used.

A downhole sucker-rod pumping unit operates as follows: If a tubing pump is used first the tubing string 3 is run into the well, the tubing pump being mounted at its lower end with automatic coupling device at the upper end of the adapter rod 15. Then the system—a fixed long flexible tube—a sliding long flexible rod with the mate automatic coupling device at the lower end of the sliding long flexible tube—is run into the tubing string 3 and connected. If an inserted pump is used first the tubing string 3 is run into the well with automatic coupling device at its lower end. Then the system—a fixed long flexible tube-a sliding long flexible rod with the installed inserted pump with the mate automatic coupling device as a collet pipe coupling (not shown) is run into the tubing string 3. In any case before running into the well at the wellhead the bucket 10 is filled with the design volume of spacer fluid 12. After the downhole sucker rod pumping unit is run into the well the tubing string 3 is attached to the production wellhead 25 at the wellhead and then to the field gathering main pipeline, the fixed long flexible tube 1 through the wellhead branch pipe is attached to the production wellhead 25 and through the channel 24 is attached to the devices (not shown) for refilling and feeding of the annular space with lubricating fluid and creation of an excess pressure in the annular space 22. The sliding long flexible rod 2 by the polished wellhead rod 20 and packing unit 18 mounted is connected to the conventional pumping unit. Moving upside the long flexible rod 2 moves simultaneously with the packing unit 11 together with the bucket 10 filled with spacer fluid 12 while borehole fluid 13 is delivered to the wellhead simultaneously with the pump 29 suction of borehole fluid 13. The spacer fluid 12 rises inside the bucket 10 due to the entry of the packing unit 6 of the diameter bigger than the pumping polished rod 8. The length of the bucket 10 and volume of spacer fluid 12 are such that in the polished rod 8 upper position the spacer fluid 12 is virtually near the upper shear of the bucket 10 but does not reach it. Moving downward the long flexible rod 2 moves simultaneously with the packing unit 11 together with the bucket 10. The level of spacer fluid 12 starts going down inside the bucket 10 due to the packing unit 6 leaving the bucket 10. The length of the bucket 10 and volume of spacer fluid 12 are such that in the lower position of the polished rod 8 the level of spacer fluid 12 is above the packing unit 6 completely covering it and protecting the seal 7 from the contact with borehole fluid 13 thus increasing its life. Having reached its lower position the long flexible rod 2 starts its upward motion and the cycle repeats.

A downhole sucker-rod progressive cavity pumping unit operates as follows: a downhole sucker-rod progressive cavity pumping unit can be run into the tubing string 3 as a single whole with the automatic coupling device on the shaft 31 of the cavity pump 32, then the system—a fixed long flexible tube—a sliding long flexible rod with the automatic coupling device is run into the tubing string 3 and connected or, as an alternative, first the tubing string 3 is run into the well then the system—a fixed long flexible tube—a sliding long flexible rod with the installed progressive cavity pump with the automatic coupling device as a collet pipe coupling (not shown) is run into the tubing string 3. After the system—a fixed long flexible tube—a sliding long flexible rod with the automatic coupling device, such as a collet pipe coupling allowing transfer of the rotation movement is run into the tubing string 3, the tubing string 3 is attached to the production wellhead 25 at the wellhead and then to the field gathering main pipeline, the fixed long flexible tube 1 through the wellhead branch pipe 40 is attached to the production wellhead 25 and through the channel 24 is attached to the device (not shown) for refilling and feeding of the annular space with lubricating fluid (a tank or a hydraulic pump) and the sliding long flexible rod 2 is attached to the actuator 35 for its rotation. If there is no lubricating fluid 23 in the annular space 22 the latter is filled with lubricating fluid 23 through the channel 24. The actuator 35 being switched on the rotation movement through the sliding long flexible rod 2 is transferred to the shaft 31 of the cavity pump 32 which starts pumping of borehole fluid 13 at the wellhead. The change in the length the long flexible rod 2 caused by its windup is allowed in the length of branch pipes.

INDUSTRIAL APPLICABILITY

The invention offered allows a considerable increase of the overhaul well life, improvement of the environment, decrease of power consumption per the unit of fluid produced. As a long-length flexible tube one can use either a new or a spent, burned-out or spliced coiled tubing. In addition, instead of a steel long flexible tube it is possible to use a reinforced hose or hose-cable, such as the one produced by the Russian company “Pskovgeokabel”. 

1. A downhole sucker-rod pumping unit, comprising: a surface power drive; a tubing string with a mounted borehole pump, said borehole pump having a driven operating element connected to a sucker rod; wherein the sucker rod comprises a fixed flexible tube and a movable flexible rod, the movable flexible rod being connected at a first end to the surface power drive by a wellhead polished rod and at a second end to the driven operating element as a plunger of the borehole pump by a pumping polished rod; an annular space between the movable flexible rod and the fixed flexible tube for receiving a lubricating fluid from a channel at a wellhead end; a wellhead pipe branch and a pumping pipe branch at respective upper and lower ends of the fixed flexible tube, the length of said branches being longer than a maximum plunger pump stroke of the borehole pump, and; a sealing unit of the pumping polished rod, said pumping polished rod connected at a lower end to a packing unit having a bucket filled with a fluid the specific weight of which is higher than that of a pumped out fluid for protecting the sealing unit of the polished rod in select positions.
 2. A downhole sucker-rod pumping unit according to claim 1, wherein the availability in the annular space for receiving the lubricating fluid from the channel creates an excess pressure.
 3. A downhole sucker-rod pumping unit according to claim 1, wherein a bypass valve is calibrated for a design pressure at the connection of the annular space with the cavity of the upturned bucket.
 4. A downhole sucker-rod pumping unit, comprising: a surface power drive; a tubing string with a mounted borehole pump, said borehole pump having a driven operating element connected to a sucker rod; wherein the sucker rod comprises a fixed flexible tube and a movable flexible rod, the movable flexible rod being connected at a first end to the surface power drive by a wellhead polished rod and at a second end to the driven operating element as a shaft of a progressing cavity by a pumping polished rod; an annular space between the movable flexible rod and the fixed flexible tube for receiving a lubricating fluid from a channel at a wellhead end; a wellhead pipe branch and a pumping pipe, an upper end of the wellhead pipe branch being attached to a sealing unit of the pumping polished rod and with an upturned bucket filled with the lubricating fluid.
 5. A downhole sucker-rod pumping unit according to claim 4, wherein the availability in the annular space for receiving the lubricating fluid from the channel creates an excess pressure.
 6. A downhole sucker-rod pumping unit according to claim 4, wherein a bypass valve is calibrated for a design pressure at the connection of the annular space with the cavity of the upturned bucket. 